Influence of Heat Pattern in Reheating Furnace on Hot Workability of 36%ni–fe Slab

Three dimensional numerical analysis model of thermal stress and deformation of slab in reheating furnace was constructed. Using this model, temperature distribution, thermal stress and deformation of 36%Ni-Fe alloy slab showing the unique thermal expansion property, called "Invar ally", were simulated. During slab reheating, the surface part of the slab is always a high temperature compared with the internal portion. The difference of temperature between surface and center parts of slab causes the difference of thermal expansion, and stress acts on each part of the slab. The magnitude and the direction of stress vary in accordance with plastic deformation through the reheating phase. Tensile stress can be generated on the surface part of the slab during heating. If the tensile stress acting on the surface part is large enough, surface defects may be easily caused. Therefore, it is suggested that attention should be paid to the heating pattern in order to avoid surface defects of 36%Ni-Fe alloy.